Spherical shaped body with aerodynamic torque ribs

ABSTRACT

1. A generally spherically shaped member having a plane of symmetry and an axis passing substantially through the geometric center of said member normal to said plane of symmetry, said member further having external aerodynamic features which will cause it, when placed into an airstream, to spin about said axis regardless of the orientation of said member relative to the airstream, said aerodynamic features including a plurality of torque ribs, each of said ribs having: AN AERODYNAMIC FORCE CENTERED ON SAID PLANE OF SYMMETRY AND EXTENDING A SHORT DISTANCE TO EITHER SIDE OF IT; A FRONT FACE HAVING A FIRST PART EXTENDING FROM ONE SIDE OF SAID AERODYNAMIC FENCE FOR A SHORT DISTANCE SUBSTANTIALLY PARALLEL TO SAID PLANE OF SYMMETRY, THEN CURVING IN A CIRCULAR RADIUS AWAY FROM SAID PLANE OF SYMMETRY INTO A SEGMENT AT AN ANGLE TO SAID PLANE OF SYMMETRY, SAID FACE FURTHER HAVING A SECOND PART EXTENDING FROM THE OTHER SIDE OF SAID AERODYNAMIC FENCE, SAID SECOND PART BEING SUBSTANTIALLY SYMMETRICAL TO SAID FIRST PART WITH REFERENCE TO SAID PLANE OF SYMMETRY; AND A REAR FACE PROVIDING A SMOOTH STREAMLINED SURFACE EXTENDING TOWARDS THE REAR AND DOWNWARD FROM THE UPPER EDGE OF SAID FRONT FACE AND MERGING WITH THE SPHERICAL SURFACE OF THE MEMBER.

United States Patent Inventor Robert S. Kensinger Minneapolis, Minn.

Appl. No. 560,707

Filed June 27,1966 Patented Oct. 12, 1971 Assignee Honeywell, Inc.

Minneapolis, Minn.

SPHERICAL SHAPED BODY WITH AERODYNAMIC TORQUE RIBS 6 Claims, 3 DrawingFigs.

U.S. Cl

Int. Cl ..F42b 25/20,

Field of Search Primary Examiner-Benjamin A. Borchelt AssistantExaminer-C. T. Jordan Attorneys-Roger W. Jensen, Charles J. Ungemach andAlbin Medved CLAIM: l. A generally spherically shaped member having aplane of symmetry and an axis passing substantially through thegeometric center of said member normal to said plane of symmetry, saidmember further having external aerodynamic features which will cause it,when placed into an airstream, to spin about said axis regardless of theorientation of said member relative to the airstream, said aerodynamicfeatures including a plurality of torque n'bs, each of said ribs having:an aerodynamic force centered on said plane of symmetry and extending ashort distance to either side of it; a front face having a first partextending from one side of said aerodynamic fence for a short distancesubstantially parallel to said plane of symmetry, then curving in acircular radius away' from said plane of symmetry into a segment at anangle to said plane of symmetry, said face further having a second partextending from the other side of said aerodynamic fence. said secondpart being substantially symmetrical to said first part with referenceto said plane of symmetry; and a rear face providing a smoothstreamlined surface extending towards the rear and downward from theupper edge of said front face and merging with the spherical surface ofthe member.

' mimiuucnzlsn 3511.930

INVENTOR. ROBERT S. KENSINGER TTORNEY SPHERICAL SHAPED BODY WITHAERODYNAMIC TORQUE RIBS The present invention pertains to fluid motionresponsive devices wherein said device or a member within said device iscaused to spin in response to the relative motion between the member andthe fluid. More particularly, the present invention provides a generallyspherically shaped member having aerodynamic features which will causeit to spin about a predetermined axis whenever the member is placed in astream of fluid or gas. The member will be caused to spin about thepredetermined axis no matter what the relative orientation of the memberand the stream may happen to be.

An example where the present invention will find application are bombsequipped with centrifugal arming fuses. Proper operation of such a bombrequires that prior to the impact with the target, the bomb must attaina certain degree of rotational velocity about a predetermined armingaxis. The aerodynamic design according to the present invention inducesthe rotation of the bomb about fixed fuse arming axis, at a ratesufficient to accomplish the arming, regardless of the bomb orientationrelative to the air stream.

The design calls for a housing member having a generally sphericalshaped outer surface and a plurality of aerodynamic torque ribsincorporated into the external design of the member to provide therequired spin rate for fuse arming. The design is symmetrical about aplane of symmetry which cuts the member into substantially two equalparts. The fuse is internally mounted with the arming axis fixed to thebomb geometric center normal to the plane of symmetry. The fuse armingrequires unidirectional spin of a predetermined angular rate about thefuse arming axis.

The aerodynamic torque rib profile is a flat front face normal to thelocal curvature of the sphere with the rear face suitably streamlined.The spanwise contour of the front face is of prime importance ingenerating all attitude spin. Each rib consists of a flat aerodynamicfence centered on the plane of symmetry and extending a short distanceto either side of it. This aerodynamic fence is substantially normal tothe local curvature of the sphere and normal to the plane of symmetry.The front face has two parts, each part extending from one side of theaerodynamic fence. The first part of the face extends from one side ofthe aerodynamic fence, for a short distance substantially parallel tothe plane of symmetry. The face is faired from the fence in a circularradius into a constant sweep back continuing to the rib tip. The secondpart of the face, extending from the other side of the aerodynamicfence, is symmetrical to the first part with reference to the plane ofsymmetry.

The bomb is released into the air stream with random orientation. Theabsolute velocity vector can be considered as two components paralleland perpendicular to the bomb plane of symmetry. Flow parallel to theplane of symmetry will produce a net torque about the fuse arming axisby virtue of the pressure drag across the torque ribs. Flow normal tothe plane of symmetry is initially deflected by the swept rib thenturned parallel to the plane of symmetry by the curved'aerodynamicfence. Reaction to the momentum change in the flow produces a torqueabout the fuse arming axis. As a consequence, the rib design produces anet torque about the arming axis regardless of the orientation relativeto the air stream. Test data show spin sensitivity to yaw attitude of l.45 to 1.0.

Prior art designs utilized either swept or unswept ribs and straightaerodynamic fences. Design data for unswept ribs shows that spin ratebegins to decrease rapidly at yaw attitudes of about 30 decreasing tozero between 70 and 90. Swept ribs and straight fence ribs are bothcapable of producing all attitude spin. However, the best swept ribdesign exhibits a spin sensitivity to yaw attitude of 4 to l and thebest straight fence design exhibits a sensitivity of 3 to 1.

It is, therefore, an object of the present invention to provide a memberwith aerodynamic features which will cause it, or when placed into astream of fluid or gas, to spin about a predetermined axis regardless ofthe orientation of said member relative to the stream.

an aerodynamic design for a bomb which will induce rotation of the bombabout a fixed fuse arming axis at a rate sufficient for armingregardless of the bomb orientation relative to the air stream.

These and further objects will become apparent to those skilled in theart upon examination of the specification, the claims, and the drawing,in which:

FIG. 1 is a view along the spin axis of a member shaped according to thepresent invention;

FIG. 2 is a view transferred to the axis of the member illustrated inFIG. 1; and

FIG. 3 is a view ofthe same member along the axis cut away at the planeof symmetry.

FIG. 1 illustrates a member 10 with a generally spherical externalsurface 11. Protruding from surface II are four aerodynamically shapedribs l2, l3, l4, and 15. A plane of symmetry dividing member 10 into twoequal halves is parallel to the surface of the drawing, and a spin axis,about which member 10 is caused to rotate, is shown in FIG. I as passingthrough the center of member 10 in a direction normal to the face of thedrawing. By referring to FIG. 2, these relationships will become moreapparent. In FIG. 2, the spin axis is shown parallel with the paper andthe plane of symmetry shown normal to the paper.

The four aerodynamic ribs characterizing the external surface of member10 are centered on the plane of symmetry and extend on each sidegenerally in the direction of the spin axis. Each rib exhibits symmetryabout the plane of symmetry and the span of the rib on each side of theplane of symmetry is more than 45 but less than of the sphericalcurvature. Each rib has a flat aerodynamic fence l7 centered on theplane of symmetry and extending a short distance to either side of it.This aerodynamic fence is generally perpendicular to the local curvatureof the member. Extending from each end of aerodynamic fence 17 is afront face 18 also substantially normal to local curvature. A front face18 extends from the end of the aerodynamic fence 17 for short distancesubstantially parallel to the plane of symmetry. It then curves in acircular radius away from the plane of symmetry toward the spin axis,and terminates somewhere between 45 and 90 away from the plane ofsymmetry. The other half of each rib is exactly symmetrical to the firsthalf. Aerodynamic fence [7 and front face 18 each have a top edge whichis substantially parallel to the local curvature. A rear fence 19connects the top edges of the front face and the aerodynamic fence witha smooth streamlined surface extending towards the rear and downwardfrom the upper edges. The top view of the rib profile can be more easilyseen in FIG. 2.

The downward slope of rear face 19, just behind the top edge ofaerodynamic fence 17, is optimal at approximately. between 17 and 18with respect to the tangent to the surface curvature at the intersectionof the plane of symmetry and the aerodynamic fence. At a lesser anglethe tendency of the air stream is to reattach to the member after it isseparated at the junction of the fence face 17 and rib face 18 with therear face 19. At an angle which is substantially larger, the efficiencyis reduced by the negative torque resulting from the air stream pressureon the rear face of the rib located on the side diametrically opposed tothe rib whose front surface is exposed to the air stream.

The contour of front face 18 can be best seen in the illustration ofFIG. 2. Face 18 starts from the end of aerodynamic fence 17 and is atfirst parallel to the plane of symmetry. The face 18 then curves in acircular radius away from the plane of symmetry into a segment onconstant angular separation from a great circle passing through thecenter of radius of the front face curvature and the spin axis. Thisconstant angle of separation is optimum between 15 to 25. An angle of 20has been chosen in a test model and has been found to give satisfactoryoperation.

The cutaway view of FIG. 3, out along the plane of symmetry, illustratesthat the member may have an internal cavity or chamber 20. When thedesign is used as a container or shell for a bomb, the internal spacecan be filled with explosive charge and a centrifugal arming fuse. Thefuse is internally mounted with the arming axis fixed to the bombgeometric center normal to the plane of symmetry along the axis of themember. In a typical fuse, the arming requires unidirectional spin ofapproximately 40 revolutions per second about the fuse arming axis.Tests have shown that the present design will allow a bomb to get thismagnitude of angular velocity after the bomb is released into an airstream with random orientation. The flow parallel to the plane symmetrywill produce a net torque about the fuse arming axis by virtue of thepressure drag across the torque rib. Flow normal to the plane ofsymmetry is initially deflected by swept n'b then turned parallel to theplane of symmetry by the curved front face. Reaction to the momentumchange in the flow produces a torque about the fuse arming axis. As aconsequence, the rib design produces a net torque about the arming axisregardless of the orientation relative to the air stream.

Many variations and embodiments are possible within the spirit of thisinvention. It is, therefore, understood that the specific embodiment ofmy invention shown here is for the purpose of illustration only, andthat my invention is limited only by the scope of the appended claims.

lclaim:

l. A generally spherically shaped member having a plane of symmetry andan axis passing substantially through the geometric center of saidmember normal to said plane of symmetry, said member further havingexternal aerodynamic features which will cause it, when placed into anair stream, to spin about said axis regardless of the orientation ofsaid member relative to the air stream, said aerodynamic featuresincluding a plurality of torque ribs, each of said ribs having anaerodynamic fence centered on said plane of symmetry and extending ashort distance to either side ofit;

a front face having a first part extending from one side of saidaerodynamic fence for a short distance substantially parallel to saidplane of symmetry, then curving in a circular radius away from saidplane of symmetry into a segment at an angle to said plane of symmetry,said face further having a second part extending from the other side ofsaid aerodynamic fence, said second part being substantially symmetricalto said first part with reference to said plane of symmetry; and

a rear face providing a smooth streamlined surface extending towards therear and downward from the upper edge of said front face and mergingwith the spherical surface of the member.

2. A generally spherically shaped member having a plane of symmetry andan axis passing substantially through the geometric center of saidmember normal to said plane of symmetry, said member further havingexternal aerodynamic features which will cause it, when placed into anair stream, to spin about said axis regardless of the orientation ofsaid member relative to the air stream, said aerodynamic featuresincluding a plurality of torque ribs, each of said ribs having:

a flat aerodynamic fence substantially normal to the local curvature ofsaid member and normal to the plane of symmetry, said fence beingcentered on said plane of symmetry and extending a short distance toeither side ofit',

a front face substantially normal to the local curvature and having anupper edge generally parallel to the local curvature, said face having afirst part extending from one side of said aerodynamic fence, for ashort distance substantially parallel to said plane of symmetry, thencurving in a circular radius away from said plane of symmetry into asegment of constant angular separation from a greater circle passingthrough said axis and the center of said circular radius, said facefurther having a second part extending from the other side of saidaerodynamic fence, said second part being symmetrical to said first partwith reference to said plane of symmetry; and

a rear face providing a smooth streamlined surface extendiqg towards therear and downward from the upper edge 0 said front face and merging withthe sphenca surface of the member.

3. Apparatus according to claim 2, wherein the constant angularseparation of said segment of said front face is more than 15 but lessthan 25.

4. Apparatus according to claim 2, wherein said member has an internalcavity.

5. Apparatus according to claim 2, wherein said member is a bomb shelland is further characterized by an internal chamber for receivingexplosive charge and a centrifugal arming fuse.

6. Apparatus according to claim 2, wherein the downward slope of saidrear face just behind the top edge of said aerodynamic fence is morethan 17 but less than l8 with respect to the tangent to the surfacecurvature at the intersection of the plane of symmetry and saidaerodynamic fence.

1. A generally spherically shaped member having a plane of symmetry andan axis passing substantially through the geometric center of saidmember normal to said plane of symmetry, said member further havingexternal aerodynamic features which will cause it, when placed into anair stream, to spin about said axis regarDless of the orientation ofsaid member relative to the air stream, said aerodynamic featuresincluding a plurality of torque ribs, each of said ribs having anaerodynamic fence centered on said plane of symmetry and extending ashort distance to either side of it; a front face having a first partextending from one side of said aerodynamic fence for a short distancesubstantially parallel to said plane of symmetry, then curving in acircular radius away from said plane of symmetry into a segment at anangle to said plane of symmetry, said face further having a second partextending from the other side of said aerodynamic fence, said secondpart being substantially symmetrical to said first part with referenceto said plane of symmetry; and a rear face providing a smoothstreamlined surface extending towards the rear and downward from theupper edge of said front face and merging with the spherical surface ofthe member.
 2. A generally spherically shaped member having a plane ofsymmetry and an axis passing substantially through the geometric centerof said member normal to said plane of symmetry, said member furtherhaving external aerodynamic features which will cause it, when placedinto an air stream, to spin about said axis regardless of theorientation of said member relative to the air stream, said aerodynamicfeatures including a plurality of torque ribs, each of said ribs having:a flat aerodynamic fence substantially normal to the local curvature ofsaid member and normal to the plane of symmetry, said fence beingcentered on said plane of symmetry and extending a short distance toeither side of it; a front face substantially normal to the localcurvature and having an upper edge generally parallel to the localcurvature, said face having a first part extending from one side of saidaerodynamic fence, for a short distance substantially parallel to saidplane of symmetry, then curving in a circular radius away from saidplane of symmetry into a segment of constant angular separation from agreater circle passing through said axis and the center of said circularradius, said face further having a second part extending from the otherside of said aerodynamic fence, said second part being symmetrical tosaid first part with reference to said plane of symmetry; and a rearface providing a smooth streamlined surface extending towards the rearand downward from the upper edge of said front face and merging with thespherical surface of the member.
 3. Apparatus according to claim 2,wherein the constant angular separation of said segment of said frontface is more than 15* but less than 25*.
 4. Apparatus according to claim2, wherein said member has an internal cavity.
 5. Apparatus according toclaim 2, wherein said member is a bomb shell and is furthercharacterized by an internal chamber for receiving explosive charge anda centrifugal arming fuse.
 6. Apparatus according to claim 2, whereinthe downward slope of said rear face just behind the top edge of saidaerodynamic fence is more than 17* but less than 18* with respect to thetangent to the surface curvature at the intersection of the plane ofsymmetry and said aerodynamic fence.